[Top] [All Lists]

RE: Last Call: draft-ietf-smime-sha2 (Using SHA2 Algorithms withCryptographic Message Syntax) to Proposed Standard

2008-02-29 14:36:31


Thanks for taking the time to review this ID. Responses are inline.


-----Original Message-----

There are obvious errors (intentionnaly left by the editor in 
order to know how many people read the document).

If I was going to leave something intentionally in the document to see if
you'd read it, then it would have been a lot better ... something like (note
this isn't an actual offer) "if you mention this sentence to me I'll buy you
a beer".  This ID is way too short to sneak in this kind of phrase.

On page 1:

The message digest algorithms are defined in and [SHS].  
                                            ^^^ Also in section 2.4:

Will remove the "and".

2.4. SHA-512 

  The SHA-256 message digest algorithm is defined in [SHS].

whereas it should be:

2.4. SHA-512 

  The SHA-512 message digest algorithm is defined in [SHS].

Will replace SHA-256 with SHA-512 in 2.4.

It would be valuable to explain why DSA cannot be used with 
SHA-384 and SHA-512.

I'll add some text.

In addition, it is not acceptable to reference in the 
*normative* references "work in progess", i.e.[ECCADD].

I'm pretty sure this is done all the time. There are 17 IDs in the RFC
editor queue with works-in-progress in normative references.

The same applies for [SHS]. The text states:

  NOTE [to be removed upon publication as an RFC]: NIST has not yet 
  finalized FIPS 186-3 and there is a chance that the draft may be 
  changed.  This may result in differences between what is documented 
  in the current version of this document and what is in the 
FIPS.  It 
  is intended to synchronize the final version of this draft with the 
  FIPS before publication as an RFC. 

The FIPS PUB 186-3 part that this ID needs has very little chance of
changing. The WG wanted this note to be safe.

There is a more substantive comment on the first paragraph of 
section 1. 
The text states:

  If an implementation chooses to support one of the algorithms 
  discussed in this document, then the implementation MUST do so as 
  described in this document. 

I believe the text should be:

  If an implementation chooses to support one of the algorithms 
  discussed in this document, then the implementation MUST do so as 
  described in [SHS]. 

The algorithms aren't defined in this document only the OIDs and where they
go in CMS ... so I still think it's actually "as described in this
document". But, Spencer suggests removing the sentences because they're not
needed and I tend to agree with him.

A small discussion in the security considerations section on 
the advantages (in particular in terms of performances versus 
security) of using one or another function from the SHA2 
family would be helpful.

I'll see if I can't get something from NIST (or at least point to it).

While I welcome this draft, everybody should take into 
consideration that, if the SHA2 family happens to be broken 
then we will be at risk. 
This should be mentioned into the security considerations section.

If an algorithm is cracked then isn't it obvious that we're in trouble?  No
other algorithm document I could find says something like this so I'm
inclined to not include this in the security considerations section.

The NESSIE program has evaluated with succces the WHIRLPOOL algorithm. 
WHIRLPOOL would be a good substitute to SHA-512 and I would 
encourage that "someone" drafts an RFC to specify OIDs for 
using WHIRLPOOL with CMS.


The IESG has received a request from the S/MIME Mail Security WG 
(smime) to consider the following document:

- 'Using SHA2 Algorithms with Cryptographic Message Syntax '
  <draft-ietf-smime-sha2-03.txt> as a Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits 
final comments on this action.  Please send substantive 
comments to the 
ietf(_at_)ietf(_dot_)org mailing lists by 2008-03-07. Exceptionally, 
comments may 
be sent to iesg(_at_)ietf(_dot_)org instead. In either case, please retain 
beginning of the Subject line to allow automated sorting.

The file can be obtained via

IESG discussion can be tracked via


Denis Pinkas

<Prev in Thread] Current Thread [Next in Thread>